1. Field of the Invention
The present invention relates to electronic components and methods for manufacturing the electronic components. The present invention particularly relates to an electronic component, such as a plate wave device using a Lamb wave or an SH wave, including a support member and a vibrating or movable portion such as a gyro or an RF switch and also relates to a method for manufacturing the electronic component. The vibrating or movable portion is levitationally supported with the support member.
2. Description of the Related Art
Conventional electronic components include support members and vibrating or movable portions using plate waves. The vibrating or movable portions are levitationally supported with the support members.
For example, Japanese Unexamined Patent Application Publication No. 2007-251910 discloses a Lamb wave device. FIG. 5 shows the Lamb wave device, which is represented by reference numeral 110, in cross section. The Lamb wave device 110 includes a reinforcing substrate 150 which is a support member and which has a recessed portion 153, a piezoelectric substrate 120 bonded to the reinforcing substrate 150, and a vibrating portion levitationally supported with the reinforcing substrate 150. The piezoelectric substrate 120 has a region spaced from the reinforcing substrate 150 with a space 154 in the recessed portion 153 located therebetween. The region carries an IDT electrode 130, first reflectors 141, and second reflectors 142.
The Lamb wave device 110 is manufactured through steps shown in FIGS. 7A to 7F. As shown in FIG. 7A, the recessed portion 153 is formed in the reinforcing substrate 150, which is made of silicon and is flat. As shown in FIG. 7B, a sacrificial layer 156 is formed in the recessed portion 153. The sacrificial layer 156 and the upper surface of a peripheral portion 151 of the reinforcing substrate 150 are smoothed by a chemical mechanical polishing (CMP) process or the like. As shown in FIG. 7C, a quartz slab 120a for forming the piezoelectric substrate 120 is bonded to the reinforcing substrate 150 by a direct bonding process, a chemical bonding process, or a bonding process using an adhesive or the like. As shown in FIG. 7D, the quartz slab 120a is polished, whereby the piezoelectric substrate 120 is formed so as to have a predetermined thickness represented by H. As shown in FIG. 7E, the IDT electrode 130 and the first and second reflectors 141 and 142 are formed on the piezoelectric substrate 120. As shown in FIG. 7F, the sacrificial layer 156 is removed, whereby the space 154 is formed. This allows the vibrating portion to be levitationally supported with the reinforcing substrate 150.
For example, PCT Japanese Translation Patent Publication No. 2002-503885 discloses a method for forming a single-crystalline thin-film. The single-crystalline thin-film is formed by the following procedure: a damaged layer is formed by implanting ions into a region of a single-crystalline substrate that is located at a predetermined depth from a surface of the single-crystalline substrate and a region of the single-crystalline substrate that is located between the damaged layer and the surface of the single-crystalline substrate is then stripped off. The method is known as an ion-slicing process. According to the ion-slicing process, the depth of a damaged layer can be varied by adjusting ion implantation parameters and a single-crystalline thin-film with a thickness on the order of micrometers can be formed.
For example, Japanese Unexamined Patent Application Publication No. 2008-54276 discloses a method for producing a piezoelectric film. FIG. 6 shows the piezoelectric film, which is represented by reference numeral 111, in cross section. The piezoelectric film 111 is produced in such a manner that a sprayed film 112 serving as a support member is formed on a rough principal surface 111a of a piezoelectric body so as to have a thickness of several hundreds of micrometers and the thickness of the piezoelectric body is reduced by polishing. The piezoelectric film 111 and the sprayed film 112 form a conjugate 101.
It is difficult to efficiently manufacture the Lamb wave device 110 because the quartz slab 120a is polished into the piezoelectric substrate 120 in such a state that the piezoelectric substrate 120 is bonded to the reinforcing substrate 150 as shown in FIG. 7C.
In order to excite a Lamb wave at an RF band with the vibrating portion of the Lamb wave device 110 shown in FIG. 5, the piezoelectric substrate 120 needs to have a thickness of several micrometers depending on the frequency of the Lamb wave. Therefore, the piezoelectric substrate 120 is fragile and is difficult to handle. This causes the problem of low product yield.
The use of a thin piezoelectric film requires a piezoelectric body and support member, which are to be bonded to each other, to have high flatness. Therefore, there is a problem in that the CMP slurry used to planarize the piezoelectric body and the support member by polishing or grinding needs to be adjusted depending on a material contained in the piezoelectric body or the support member. In the case of using an adhesive or the like to bond the piezoelectric body to an insulating body, there are problems with the elasticity of the adhesive and the change thereof with time. In the case where the piezoelectric body and the support member are bonded to each other at room temperature, expensive apparatuses such as a surface-cleaning apparatus and a vacuum chamber are necessary. Such apparatuses have low throughput.